Viscous coupled cooling fans.

Cowling around fan to direct all that hot air right onto the coupling ?

Standard fitting on the car - and in good condition. But you wouldn't want to restrict the airflow through the rad at speed. I only have this problem in heavy traffic.

Why not just do the job properly and unbolt that antequated shit that's sapping fuel and power and couple the fans up to a proper temp sensor? Pacet do a kit that fits in the top rad hose.

I ditched the viscous fan on the Capri very early on. Best decision ever.

Bin it. Get a Kenlowe or Pacet kit. Capper was horrendous at getting hot in traffic and not getting warm enough in NSL driving. Now it's got an adjustable Kenlowe kit fitted, it warms up quicker in winter, runs warmer on runs and the temp doesn't go any higher than I want it to.

Best £100-£150 you'll spend.

I wouldn't need such a bodge as the rad is already fitted with a switch for the existing auxiliary fans.

The Capri didn't have a varying lock type. Which are very efficient and fitted by just about every new car maker. It makes no sense to drive an alternator with a belt then use the output from that to drive an electric fan. You might as well drive an efficient fan system directly. Oh - the other thing is most electric fans simply aren't as powerful.

They have a clutch or something inside. If you regularly hammer it they screw up, if you dont then they screw up anyway. They are big and never should totally lock or at high revs you will move by reving the car! Anyway they are almost always buggered and freewheel at all temperatures. Bin. You dont need the power. If driving does not cool it then you have other problems. If idling or reving at a standstill then even an average leccy fan keeps up.

Exactly. The only time I knew that the fuse had blown on my rad fan was when I was sat for a long time in stop/start traffic on Scarboro seafront and it got way hot.

A viscous coupling. Closer to a torque convertor than clutch.

Err, how can you hammer something like that?

They may not fully lock but get close to it. And yes - at lock they move a

Bollocks. Just about every large modern car has one and most buses, etc.

Oh yes you do in heavy slow traffic.

You don't need any fan at speed. On a conventional front rad car.

Not in my case. A combination is the best solution.

Easy. If you rev the nuts off it all the time the viscose coupling needs to slip more and they soon die. And they have some kind of clutch too, as a high temp safeguard for when its really hot controlled by a internal bi metalic thingy. If you drive everywhere at high rpm the things screw up. At first they just freewheel when buggered.. But then while idling the car can get too hot and the internal heat sensitive clutch or whatever it is that grabs suddenly if you hold a blade still for ten mins at idle spins the thing at engine speed. Rev it hard now and the internals weld up as it slips and you get a very loud fixed fan and a noticibly slower car!

They DO lock after the thing dies eventually. They sieze up and rotate at engine speed after a few months freewheeling doing bugger all.

If you say so. My last 6 vehicles, my dads car, my mates cars all have a simple thermostatic electric one nowadays.

Yes but as all the simple electric faned cars prove a small leccy fan is fine.

You dont say...

Your case is different to most cars then.

You really don't understand their principle. They react to the temperature of the air 'hitting' them via the rad. If below a certain temperature they simply near idle. When the rad gets very hot the air hitting the bi-metallic spiral on the front of the device rotates a valve which progressively reduces the 'slip' of the coupling causing the fan to run faster therefore cooling the rad which in turn operates the spiral and increases the slip - acting as a sort of thermostatic control. And in the locked state you will get an increase in fan noise - it means it's doing its job and cooling the rad. Nor will it use any more power than a similar capacity electric one - it may well actual consume less.

Yep. I know...

If below a certain temperature they

Correct or freewheel...

When the rad gets very hot the air hitting the

Yes I know... I took many ford sierra ones apart with a hammer to figure out why they die in two stages...

And in the

Correct.

Or in the siezed state meaning its doing its job too well and causes the belt to slip and squeel and the car to move as about 15 bhp gets used up by the 6k big fan!

When WORKING (and slipping) and on a hot engine they turn faster. They they dont they ONLY freewheel no mater what temp the air hitting them is. They use a bit more engine power but they are not supposed to go round at engine speed. And when you rev the knackesr off one all day thats what happens. They physically SIEZE. After that they ALWAYS turn at engine speed even when cold until you get pissed off with a slow noisey car and /or the belt gives up.

Nor will it use any more power than a similar

When working correctly yes I totally agree!

Yes - they will actually be driven by airflow under certain conditions.

Well any device can fail.

So replace it. Electric fans fail too. More often in my experience. I've had more than half a dozen cars with temperature controlled viscous fans and only had one fail locked. The noise would prompt anyone with mechanical sympathies not to rev the nuts off it until fixed. When they're working properly they only ever lock in heavy slow traffic where you'd not be revving the nuts off a car anyway.

Other thing is many cars won't have the spare electrical capacity to drive a similar capacity replacement electric one - it will take a deal of current. Of course many will just fit a small one and think that ok. The amount of cooling a large engine running AC in heavy slow traffic needs is considerable - hence most using a combination of viscous fan and electric.